The target for the convolution parameter. Must be one of GL_CONVOLUTION_1D, GL_CONVOLUTION_2D, or GL_SEPARABLE_2D.

pname

The parameter to be set. Must be one of GL_CONVOLUTION_BORDER_MODE, GL_CONVOLUTION_BORDER_COLOR, GL_CONVOLUTION_FILTER_SCALE, or GL_CONVOLUTION_FILTER_BIAS.

params

The parameter value. If pnamev is GL_CONVOLUTION_BORDER_MODE, paramsv must be one of GL_REDUCE, GL_CONSTANT_BORDER, or GL_REPLICATE_BORDER. Otherwise, must be a vector of four values (for red, green, blue, and alpha, respectively) to be used for scaling (when pnamev is GL_CONVOLUTION_FILTER_SCALE), or biasing (when pnamev is GL_CONVOLUTION_FILTER_BIAS) a convolution filter kernel or setting the constant border color (when pnamev is GL_CONVOLUTION_BORDER_COLOR.

target selects the convolution filter to be affected: GL_CONVOLUTION_1D, GL_CONVOLUTION_2D, or GL_SEPARABLE_2D for the 1D, 2D, or separable 2D filter, respectively.

pname selects the parameter to be changed. GL_CONVOLUTION_FILTER_SCALE and GL_CONVOLUTION_FILTER_BIAS affect the definition of the convolution filter kernel; see glConvolutionFilter1D(), glConvolutionFilter2D(), and glSeparableFilter2D() for details. In these cases, paramsv is an array of four values to be applied to red, green, blue, and alpha values, respectively. The initial value for GL_CONVOLUTION_FILTER_SCALE is (1, 1, 1, 1), and the initial value for GL_CONVOLUTION_FILTER_BIAS is (0, 0, 0, 0).

The image resulting from convolution is smaller than the source image. If the filter width is Wf and height is Hf, and the source image width is Ws and height is Hs, then the convolved image width will be Ws - Wf + 1 and height will be Hs - Hf + 1. (If this reduction would generate an image with zero or negative width and/or height, the output is simply null, with no error generated.) The coordinates of the image resulting from convolution are zero through Ws - Wf in width and zero through Hs - Hf in height.

GL_CONSTANT_BORDER

The image resulting from convolution is the same size as the source image, and processed as if the source image were surrounded by pixels with their color specified by the GL_CONVOLUTION_BORDER_COLOR.

GL_REPLICATE_BORDER

The image resulting from convolution is the same size as the source image, and processed as if the outermost pixel on the border of the source image were replicated.

glConvolutionParameter is present only if ARB_imaging is returned when glGetString() is called with an argument of GL_EXTENSIONS.

In cases where errors can result from the specification of invalid image dimensions, it is the dimensions after convolution that are tested, not the dimensions of the source image. For example, glTexImage1D() requires power-of-two image size. When GL_REDUCE border mode is in effect, the source image must be larger than the final power-of-two size by one less than the size of the 1D filter kernel.